782 



In order to show some of Ihe most important causes of errors, 

 I shall point out, that several of the species, which have been found on 

 the coasts of Greenland, the Færoes and Iceland, according to papers 

 pubHshed during the latest years, e. g. Rosenvinge's on the marine 

 algæ of Greenland, my own paper on the Færoese marine algæ, and 

 lastly Jonsson's on the marine algæ of Iceland, also will be found 

 in the surrounding countries on renewed investigations. In Batter's 

 recently published list of the marine algæ of Great Britain we thus find 

 many of Rosenvinge's new^ Greenlandic species mentioned. Another 

 source of error is naturally the different authors' varying opinions of 

 species; and even if we try ever so conscientiously to make out the 

 different synonyms, there are still, according to our present know- 

 ledge, a great many genera — I need only mention promiscuously 

 Lithothamnion, Sphacelaria, Mijrionema, Acrosiphonia, Spongomorpha, 

 Cladophora, Enteromorpha, Ulothrix — of which it is almost impos- 

 sible to make any statement with cerlainty. On the whole, it is espe- 

 cially the classification of the Chlorophyceæ which causes the greatest 

 difficulties ; and as the piants of this group thrive in very extreme 

 conditions, which quality they have in common with the Cyano- 

 phijceæ, for instance they are well fitted for standing a mixture 

 with fresh water, it would perhaps be most correct to side with 

 Kuckuck who says (56, p. 10): »Bei pflanzengeographischstati- 

 stischen Zusammenstellungen scheinen mir daher die Chlorophy- 

 ceen und Cyanophyceen eher geeignet, das Resultat zu triiben als 

 zu klåren, und aus diesem Grunde will ich auch hier von einer 

 Beriicksichtigung jener Pflanzengruppe absehen.« But as it cannot 

 be denied, however. that there are several species, even among the 

 Chlorophyceæ and Cyanophyceæ, which are of no small importance 

 from a phyto-geographical point of view, I have used them here 

 as far as possible for the sake of comparison. 



Further, it is naturally of great importance in a comparison of 

 this nature, to exclude the species which by mistake have been in- 

 cluded previously in the flora of a country, when closer investiga- 

 tions have shown that it is only by erroneous determination or for 

 some other reason, that they have been included, and thus do not 

 belong to the flora at all. As to Greenland, so man}' species had 

 been incorrectly admitted, according to Rosen vinge (71, p. 154) 

 that the phyto-geographical character of the algæ -flora has been 

 essentially altered by their omission; also, with regard to the 

 Færoes we have been obliged to exclude several of the species 



